Stiffness and excluded-volume effects in polymer chains

In order to examine the correlation between stiffness and excluded-volume effects in polymer chains, polymethylene-like rotational isomeric state chains with excluded volume are simulated and their mean-square radii of gyration are evaluated by Monte Carlo methods. The present results and also experimental data for ordinary flexible chains may well be explained by the Kratky–Porod worm-like chain, or more generally the helical worm-like chain, with the excluded-volume effects incorporated in the Yamakawa–Stockmayer scheme. For typical stiff chains with excluded volume, however, there is clear disagreement between their theory and experiment, and the problem remains unsolved.